GCN Circulars
GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search
To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.
Advanced Search Examples (click to copy):
subject:"Swift"body:"GRB"submitter:"Judith Racusin"- GRB 251130B: TERI Gamma-ray detection
- GRB 260208A: TERI Gamma-ray detection
- GRB 260302A: Fermi GBM Final Real-time Localization
- EP260227a: Mondy optical observations
- GRB 260228A: CAHA 2.2m telescope optical upper limit
- GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- EP260227a: Mephisto optical detection
- GRID detection of GRB 260225D
- EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
- EP260227a: further LCO observations
- EP260227a: SVOM/VT optical observation
- GRB 260228A: SVOM/VT optical upper limits
- GRB 260225D: SVOM/GRM observation
- EP260227A: 3.6m DOT optical afterglow detection
- GRB 260225B: SVOM/GRM observation
- GRB 260228A: SVOM detection of a burst
- EP260227a: FTW optical and NIR observations
- EP260227a: Liverpool Telescope optical observations
- EP260227a: LCOGT Optical Observations
- GRB 260226A: Asiago r-band upper limit
- EP260227a: Thai National Telescope observations
- EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
- EP260227a: Liverpool Telescope observations
- EP260227a: COLIBRÍ optical observations
- EP260227a: NOT optical observations
- GRB 260225A: SVOM/VT optical continued observations and upper limit
- GRID detection of GRB 260223A
- EP260227a: Global MASTER-Net observations report
- EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
- The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
- EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
- IceCube cascade alert 142200_1517143 retraction
- GRB 260226A: Insight-HXMT/HE detection of the very bright burst
- Konus-Wind detection of GRB 260226A
- GRB 260223A: 7DT detection and Medium-band SED of Afterglow
- EP260214a: VLT/FORS2 optical observations
- GRB 260225A: WINTER J-band upper limit
- GRB 260226A: CALET Gamma-Ray Burst Monitor detection
- GRB 260226A: COLIBRÍ optical upper limits
- GRB 260226A: LCOGT Optical Upper Limit
- EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
- GRB 260225D: Glowbug gamma-ray detection of a likely short burst
- GRB 260226A: Glowbug gamma-ray detection
- GRB 260226A: NuSTAR detection of bright prompt emission
- GRB 260226A : GROWTH-India Telescope optical observations
- GRB 260226A: LAST optical upper limit
- GRB 260226A: Fermi GBM observation
- GRB 260226A: Fermi-LAT refined analysis
- The EP-WXT trigger 01709258652 is likely a flaring star
- LAT GRB260226.44: Global MASTER-Net observations report
- Fermi GRB 260226A: Global MASTER-Net observations report
- GRB 260226A: AstroSat CZTI detection of bright long burst
- EP260214a: VLA 6 GHz detection
- GRB 260226A: Fermi-LAT detection of a bright burst
- GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
- EP260224a: LCO optical upper limits
- GRB260225A: SVOM/ECLAIRs refined position
- GRB 260226A: Fermi GBM Final Real-time Localization
- GRB 260225A: EP-FXT follow-up observation
- GRB 260225A: SVOM/VT optical observation
- GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
- GRB 260225C: Fermi GBM Final Real-time Localization
- GRB 260223A: Fermi GBM Observation
- GRB 260225A: SVOM/VT optical upper limits
- GRB 260225B: Fermi GBM Final Real-time Localization
- EP260126a: VLA 6 GHz detection
- EP260223a: Liverpool Telescope upper limits
- GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
- GRB 260225A: SVOM detection of a burst
- EP260224a: Einstein Probe detection of an X-ray transient
- EP 260225.148: COLIBRÍ Confirmation of flaring star
- EP260223a: Xinglong optical upper limit
- The EP-WXT trigger 01709258631 is likely a flaring star
- GRB 260223A: Glowbug gamma-ray detection
- EP260213a: Mephisto optical upper limits
- EP260223a: EP-FXT follow-up observation
- sb26021801: SVOM/VT optical upper limits
- GRB 260223A: COLIBRÍ optical afterglow decay confirmation
- sb26021801: SVOM/C-GFT upper limit
- EP260223a: COLIBRÍ optical upper limits
- EP260223a: Einstein Probe detection of an X-ray transient
- GRB 260223A: SVOM/VT optical observation
- GRB 260223A: SVOM/GRM observation
- GRB 260223A: COLIBRÍ further optical observations and a brightening
- EP260221a: Optical upper limit with Kinder observations
- GRB 260223A: COLIBRÍ optical observations
- GRB 260223A: DDOTI Optical Candidate
- GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
- Fermi GRB 260223A: Global MASTER-Net observations report
- GRB 260223A: Fermi GBM Final Real-time Localization
- EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
- EP260221a: COLIBRÍ optical counterpart candidate
- EP260221a: Gemini South z-band upper limit
- GRB 260222A: Fermi GBM Final Real-time Localization
- EP260221a: Global MASTER-Net observations report
- EP260221a: EP-FXT follow-up observation
- Fermi GRB 260221B: Global MASTER-Net observations report
- GRB 260221B: Fermi GBM Final Real-time Localization
- EP-WXT01709258519: Xinglong optical upper limit
- EP260221a: Xinglong optical upper limit